Killer claws or climbing crampons?

I still remember the first time watching Jurassic Park as a kid. Watching the raptors leaping on to their prey, hooking and slashing away with their lethal sickle claws. The annoying “six foot turkey” kid’s face as Alan Grant totally pwned him over just how a raptor would slice him open before devouring him alive. These were pretty memorable moments for me, and the vision of raptors as vicious little butchers.

But did raptors really disembowel their prey Freddy Krueger style, or was there a little more finesse? There has been a long-standing debate in palaeontology over what exactly raptors like Velociraptor and Deinonychus might have actually used their big claws for. The glorified version of it slashing out and ripping prey apart with disemboweling strikes, or more like a modern hawk or eagle, leaping on to its victim and pinning it down while gripping it with its large claws. Other studies have suggested Deinonychus used its claws like crampons, delivering small puncture wounds to their prey while climbing on them. The point is, you are alive when they start to eat you.

There have been many methods used to analyse the function of Deinonychus’ killer claws, from robots to comparisons with modern cassowaries. Now, a new study by Peter Bishop has used reconstructed muscle and skeleton modelling to offer a new perspective. By using three-dimensional models, and the known properties of the muscles, tendons, and bones, the forces associated with the claws can be assessed in a quantitative manner.

Using mathematical models, Bishop was able to simulate the factors that would provide maximum force at the tip of the claw, and therefore what function it most likely possessed. The models showed that if Deinonychus adopted more of a crouching posture, then this increased the claw forces. However, even at the higher end of things, these forces remained relatively small.

This means that the claws were not likely to be too useful in the old slash and smash approach, as they just were not strong enough. However, they were still likely to be useful in grasping on to small prey, and restraining them while the teeth did their work. This behaviour has been seen in other dinosaurs too, such as the famed ‘fighting dinosaurs’ specimen, in which Velociraptor and Protoceratops were frozen in death’s embrace, with the former gripping on to the other with its claws. Still, the thought of a 170kg eagle is pretty terrifying.

Reference

Bishop PJ. 2019. Testing the function of dromaeosaurid (Dinosauria, Theropoda) ‘sickle claws’ through musculoskeletal modelling and optimization. PeerJ 7:e7577 https://doi.org/10.7717/peerj.7577